Acinetobacter sp. Tol 5 exhibits an autoagglutinating nature and noteworthy adhesiveness to various abiotic surfaces from hydrophobic plastics to hydrophilic glass and stainless steel1). Tol 5 cells have at least three types of peritrichate bacterionanofibers2). These are type 1 fimbria, Fil fimbria, and the novel trimeric autotransporter adhesin (TAA) designated AtaA (Acinetobacter TAA). Among them, AtaA is responsible for the adhesive nature of Tol 53). Unlike adhesion of usual bacteria forming biofilms, AtaA mediates adhesion of resting cells, independent of cell growth. Analyses of the adhesion process under optical microscopes suggested that autoagglutination of bacterial cells mediated by AtaA greatly contribute to cell immobilization onto material surfaces.
AtaA consists of 3,630 amino acid residues, which makes it the largest TAAs known to date. Although AtaA follows the general N-terminus-head-stalk-membrane anchor-C-terminus organization of TAAs, an additional head domain localizes in the C-terminal region. The stalk domain of AtaA is notably longer than that of other TAAs and contains peptide repeats that are mosaically arranged. TAAs have been reported to mediate bacterial adhesion to host cells and/or extracellular matrix proteins, and autoagglutination4). However, there has been no report about such nonspecific, high adhesiveness to abiotic surfaces as AtaA mediates. This adhesion property can be conferred to other bacteria by transformation with the ataA gene.
For characterization of the AtaA passenger domain (PSD), which is translocated and displayed at the cell surface through the C-terminal anchor domain, a HRV3C protease recognition site was inserted at the base of the PSD, which was cut down for separation and purification. The fibrous structure of the PSD was observed under a transmission electron micrograph (TEM). The stability profiles of the PSD against heat and pH shift were analyzed by circular dichroism (CD) spectrometer and TEM. Affinity of the AtaA PSD to the abiotic surface was also measured using a quartz crystal microbalance (QCM) apparatus.
References:
1) M. Ishikawa, K. Shigemori, A. Suzuki, K. Hori, J. Biosci. Bioeng., 113, 719-725 (2012).
2) K. Hori, M. Ishikawa, M. Yamada, A. Higuchi, et al., J. Biosci. Bioeng., 111 31-36 (2011).
3) M. Ishikawa, H. Nakatani, K. Hori, PLoS One, 7, e48830 (2012).
4) D. Linke, T. Riess, IB. Autenrieth, et al., Trends Microbiol., 14, 1251-1256 (2006).